In the past, for example, a power supply device including LED elements as loads rectifies an alternating-current power supply with a rectifying circuit, converts a rectified direct-current voltage by turning on and off switching elements of a power-supply-voltage converting circuit, and supplies the direct-current voltage to the LED elements to turn on the LED elements.
It is known that noise superimposed on a power supply voltage according to a switching operation of the switching elements leaks to the alternating-current power supply side and affects other electric appliances connected to the alternating-current power supply. Therefore, a filter circuit for noise prevention for reducing noise is often provided between the alternating-current power supply and the rectifying circuit.
It is proposed to separately provide the rectifying circuit and the power-supply-voltage converting circuit for each of plural lamps and change, at random, switching frequencies for turning on and off the switching elements of at least one power-supply-voltage converting circuits to thereby reduce noise intensity as a whole.
An output of a luminaire including the LED elements has been increased. Electric power converted by the power-supply-voltage converting circuit of the power supply device increases according to the increase in the output. Noise leaking from the power supply device to an alternating-current power supply side also tends to increase.
Therefore, in the case of the filter circuit for noise prevention, unless a large filter circuit for noise prevention is used, a noise prevention effect is insufficient.
When the switching frequencies of the switching elements are changed at random, the circuit including the switching elements is complicated. It is likely that the degree of brightness, which is the output of the luminaire, changes according to the change in the switching frequencies.
Therefore, it is an object of the present invention to provide a power supply device that can reduce, with a simple configuration, noise intensity while keeping an output of loads fixed and a luminaire including the power supply device.